The present invention generally relates to a tractor and a trailer combination, and more particularly to a tractor and trailer combination involving an electric trailer refrigeration unit that enables a functional trailer rotating angle with respect to the tractor during a tractor turning operation.
In a typical situation, a common trailer refrigeration unit is installed on the trailer together with a diesel engine and its own diesel tank for the unit power supply. Therefore, the refrigeration unit operation is independent from the tractor with no requirements on connection between the tractor and the unit. The connection between a tractor and a trailer is provided by coiled and stretchable hoses and cables. The tractor has a pneumatic power braking system connected to a braking system of the trailer. This pneumatic system has one or more air pressure outlets connected with hoses. These hoses transmit the effects of the air pressure of the braking system from the tractor to the braking system of the trailer. Air hoses used for the described purposes are usually light-weight and they float between the tractor and the trailer. Power for the board DC voltage on the trailer is also provided by an electric cable from the tractor. These electrical cables transfer only low voltage (12 or 24 V DC) and they also do not have any special demands on the connection between the tractor and the trailer. Furthermore, these hoses and cables are coiled (i.e., spiral shaped) and stretchable in order to accommodate the demanded trailer rotating angle during turning operations. For example, the common uncoiled length of these cables and hoses is 6 meters to ensure this requirement. The coiled and stretchable cables and hoses retract to a length substantially shorter than the 6 meters such that when the tractor and trailer are aligned, the cables and hoses are shortened such that they float and do not drop in a slack condition and interfere with the coupling between the tractor and the trailer.